1. Field of the Invention
The present invention relates to telephony systems in general, and to methods of collecting data within such systems for purposes of accounting and billing subscribers and users of the telephony and the like systems. More particularly still, it relates to methods of collecting and communicating data respecting redirected telephone calls. More particularly still, it relates to such data in the case of calls originated from an end (switching) office (EO) to a telephone number that had been ported from one EO to another EO. Number portability (NP)and local number portability (LNP) are an inevitable fact of telephony in the present environment of competition between service providers.
2. Related Art
Toll call rating today is based primarily on time and distance. The AMA (automatic message accounting) record includes the call duration (time) and both the calling and called NPA-NXXs (meaning the digits of numbering plan areas plus the three digits of the office code) from which the V/H (Vertical and Horizontal) coordinates of the calling and called rate centres are determined. From the V/H coordinates, the distance and distance band are calculated. From the distance band the call rate is determined.
When new NXXs are introduced on switches or rate centres are modified, all carriers are advised in advance so that necessary trunking translations and billing process adjustments can be made. Currently the LERG (local exchange routing guide) NPA-NXX designations are geographically fixed and each has a set of V/H coordinates for billing purposes. The frequency of such NPA-NXX additions/changes is at present relatively low.
The geographically significant LERG designated NPA-NXX codes are general used as the basis for distance calculations and toll call rating by downstream operations systems. In situations where calls are redirected, either the redirecting party pays or special arrangements are made for billing. There is no vehicle to return the redirected destination information back through the network for billing purposes. In `calling party pays` situations, end-user AMA information, such as the called destination, is typically captured near the head-end of the call. However, some calls may be subsequently redirected to a different (toll) destination (as in the case of LNP with location portability).
If the originating switch redirects the call to a destination other than that dialed, then it can include the new destination routing number in the AMA record for toll calls and the call can be accurately billed. However, if the call is redirected at an intermediate switching point, the prime (upstream) AMA switches (typically the originating switch, access tandem or first IXC tandem) may not have complete destination information for accurate call rating. The absence of complete call rating information in the AMA records for redirected calls will complicate downstream processing. Without this information, the process would have to correlate switch AMA information from more than one source or process partial AMA information against other databases to rate redirected calls. In the case of "real time" billing systems, a technique will be required to retrieve appropriate redirection information quickly.